The present invention relates generally to horizontal boring tool applications and, more particularly, to systems, arrangements and methods for establishing positions of locating field detectors and for path mapping within a region for the purpose of tracking the position of and/or guiding an underground boring tool which emits a locating field as it later progresses through the region during drilling operations. A selected flux pathline steering technique is also introduced.
It should be appreciated that prior art systems for use in locating an underground boring tool primarily employ walk-over locator arrangements as disclosed, for example, in U.S. Pat. No. 5,337,002 which is assigned commonly with the present application. Inasmuch as Applicant is unaware of any prior art systems utilizing locating field detectors in the manner described in the parent of the instant application, the present application represents an advance which is particularly well suited for use with the systems and arrangements disclosed in the parent case. While the detector locating techniques disclosed in the parent case remain effective, the arrangements and method disclosed below are remarkably convenient and highly effective for their intended purpose, as will be seen.
As will be described in more detail hereinafter, there are disclosed herein arrangements, specific apparatus and associated methods for use in establishing the positions of locating field detectors and for path mapping within a region for the purpose of tracking and/or guiding the movement of an underground boring tool.
In one aspect of the invention, an improvement is provided forming part of an arrangement for tracking the position and/or guiding the boring tool using an electromagnetic locating signal which is transmitted from the boring tool as the boring tool moves through the ground, the improvement comprising at least two detectors located at fixed positions within the region, each being operable in a transmit mode and in a receive mode such that each one of the detectors in the transmit mode is able to transmit a relative locating signal to the other detector for use in determining the relative position of one detector in relation to the other and such that both detectors receive the electromagnetic locating signal in the receive mode for use in determining the position of the boring tool within the region.
In another aspect of the invention, at least two detectors initially receive the electromagnetic locating signal with the boring tool at a first position to produce a first subset of electromagnetic data and then the detectors receive the electromagnetic locating signal with the boring tool at a second position to produce a second subset of electromagnetic data. Thereafter, processing means combines the first and second subsets of electromagnetic data to produce an overall set of electromagnetic data for use, along with the established relative position between the detectors in determining the absolute positions of the detectors in the region.
In still another aspect of the present invention, the detectors are able to receive the electromagnetic locating signal in the receive mode within a dipole range from the boring tool and are able to receive the relative locating signal within a relative range from a detector that is in the transmit mode. Additional detectors may be provided for purposes including extending drilling range or further improving system accuracy. Accordingly, at least one additional detector is positioned in the region such that the additional detector may be out of the dipole range from the boring tool, but within the relative range of at least a first specific one of the other detectors, the absolute position of which is known in the region such that, with one of either the first specific detector or the additional detector in transmit mode and the other one of either the additional detector or the first specific detector receiving the relative locating signal, the relative position of the additional detector is determinable in relation to the known position of the first specific detector so that, in conjunction with the known position of the first specific detector, the absolute position of the additional receiver is established within the region.
In yet another aspect of the present invention, a system is provided including at least two above ground detectors for sensing the locating signal transmitted from the boring tool as part of an above ground arrangement, each of the detectors is configured for receiving the locating signal. The detectors are located at initial positions in the region within a dipole range of the electromagnetic locating signal transmitted from the boring tool at a first, start position. The locating signal is received by the detectors with the boring tool first at its start position to produce a first set of electromagnetic data. The boring tool is then moved to a second position. The electromagnetic locating signal is again received using the detectors with the boring tool at its second position to produce a second set of electromagnetic data. Absolute positions of the detectors within the region are then determined using certain information including the first and second sets of electromagnetic data in a predetermined way. In accordance with one feature of the present invention, one or more additional subsets of electromagnetic data may be produced at one or more additional positions of the boring tool. The additional subsets of electromagnetic data are then used in determining the absolute positions of the detectors as part of the overall electromagnetic data. Each additional position of the boring tool shifts the balance from unknown values to known values by at least one value. Accordingly, given a sufficient number of additional positions of the boring tool, the absolute positions of the detectors may be determined based solely on electromagnetic data.
In accordance with the aspect of the invention immediately above, the drilling range of the system may be extended by moving the detectors to new positions beyond their initial positions within the region. Electromagnetic data is generated with the boring tool at some subsequent position which may be known since the boring tool may be tracked up to this subsequent position with the detectors at their initial locations. The boring tool may then be moved to an additional subsequent position to generate further electromagnetic data. The electromagnetic data gathered at these subsequent positions of the boring tool may then be used in determining the new positions of the detectors such that tracking and/or guiding of the boring tool may then be performed in an area which is out of range of the detectors at their initial positions.
In accordance with another feature of the present invention a mapping tool is provided as part of the system for tracking the position and/or guiding a boring tool in the ground as the boring tool moves along an underground path which lies within a region. At least two above ground detectors are provided, each detector being configured for receiving the electromagnetic locating signal. With the boring tool at a start position, the above ground detectors are located at initial fixed positions within dipole range of the boring tool in an initial portion of the region for receiving the electromagnetic locating signal as the boring tool is later guided along an initial segment of the intended path within the dipole range of the boring tool. Without moving the boring tool from its start position, absolute positions of the detectors are determined within the initial portion of the region. Thereafter, the initial segment of the intended path is mapped through the initial portion of the region in a particular way using the detectors. Mapping/drilling range may be extended by moving the detectors in a predetermined way to new locations within an adjacent, new portion of the region including an adjacent, new segment of the intended path and establishing absolute positions of the detectors within the adjacent portion of the region. Thereafter, without moving the boring tool from its start position, the new segment of the intended path may be mapped in essentially the same manner as the initial segment through the new portion of the region through which the boring tool will later pass after having passed through the initial portion of the region. Mapping may be further extended by repeatedly locating the detectors in additional adjacent portions of the region and mapping the intended path through segments in these additional adjacent portions. Alternatively, each segment along the intended path may be mapped immediately prior to drilling. That is, each segment is mapped and drilled prior to mapping and drilling of the next segment along the intended path.
In one configuration, advantages of the present invention are provided in a system including a transceiver detector located at one fixed position within the drilling region. The transceiver detector is configured for transmitting a relative locating signal in a setup mode and for receiving the electromagnetic locating signal from the boring tool in a tracking mode for use in establishing the position of the boring tool. At least one receiver detector is provided at another fixed position within the region. The receiver detector is configured for receiving the relative locating signal in the setup mode such that the position of the receiver detector can be established relative to the position of the transceiver detector based on the relative locating signal and for receiving the electromagnetic locating signal in the tracking mode for use in establishing the position of the boring tool concurrent with a drilling operation.
In an additional aspect of the present invention, one above ground detector is provided configured for receiving the locating signal at a location within a dipole range of the locating signal transmitted from the boring tool at a first, start position. Before moving the boring tool to a second position, the locating signal is received at the first position to produce a first set of electromagnetic data. A second set of electromagnetic data is then produced with the boring tool at the second position. The absolute positions of the detector and the boring tool within the region are determined using certain information including the first and second sets of electromagnetic data in a predetermined way. In one feature, the distance between the first and second positions is measured and used as at least part of the certain information.
In a further aspect of the present invention, an improvement is provided for steering the boring tool using an electromagnetic locating signal which is transmitted from the boring tool as the boring tool moves through the ground. The improvement includes establishing a target location towards which the boring tool is to be steered and, thereafter, selecting a flux pathline extending between the boring tool and the target location such that a constant flux ratio between a vertical component of the locating field in a vertical direction and a horizontal component of the locating field in a horizontal direction is present along the selected flux pathline. The boring tool is then guided along the selected flux pathline to the target location.